dating scan measure 2 weeks back

Brittany

According to my lmp may 3rd 2018, I was 11 weeks 4 days as of today. I had my first sonogram today and my dating scan measured me at 9 weeks 4 days. I am just a little confused. Also my lo heartbeat is 178. my daughter heartbeat was 140s and no symptoms. this baby morning sickness and diarrhea, headaches here and there, fatigue of course. It's so different than my daughter's. my husband and I want a boy. what do y'all think?